In a chemical production process in which reaction product solids are formed in a reactor vessel, a gaseous outflow from the reactor vessel may be exhausted to accommodate a continuing inflow of reactant feed gas during the reaction, the feed gas possibly including a large volume of inert carrier gas. Reaction product solids may become entrained in the gaseous outflow, particularly where agitation of the reactants is provided. If the portion of the reaction product entrained in the gaseous outflow is not recovered, the effective yield of the reaction is reduced, productivity is decreased and production costs are increased.
Reduced product yield through loss of reaction product solids entrained in a gaseous outflow from the reactor vessel is encountered, for example, in a known production process for silicon nitride precursor. Silicon nitride-based ceramics are considered amongst the toughest of the monolithic ceramics for use above 1000.degree. C. The toughness is thought to be due primarily to a high degree of grain interlocking which can be developed from appropriate powders. Silicon nitride-based ceramics can be formed to near-net shape in a pressureless sintering operation from powders having the necessary characteristics. Silicon nitride ceramics are, therefore, prime candidates for light weight engine components, for example, in which toughness is needed together with high temperature wear resistance.
The above mentioned method for making silicon nitride precursor is taught in U.S. Pat. No. 4,732,746 to Crosbie et al. The Crosbie et al patent is directed particularly to production of silicon imide solids as a silicon nitride precursor. To prevent or reduce carbon contamination, an inert carrier gas, preferably nitrogen or argon, is used to bring silicon halide, preferably SiCl.sub.4, vapor into contact with liquid ammonia. The reaction produces a mixture of precipitated silicon imide in liquid ammonia having dissolved ammonium halide. The silicon halide vapor is brought into reaction with the liquid ammonia by means of providing a sustained inflow to the reaction situs of a reactant feed gas comprising silicon halide vapor and the inert carrier gas. A gaseous outflow comprising primarily residual carrier gas and a certain amount of vaporized ammonia is released from the reaction situs to accommodate the continuing inflow of fresh reactant feed gas. The reaction situs preferably is agitated during the reaction. A certain fraction of the silicon nitride precursor precipitate may be entrained in the gaseous outflow from the reaction situs. The loss of such entrained solids reduces the effective reaction yield.
It would be desirable in numerous reaction schemes and production processes, including particularly, for example, the production of silicon nitride precursor in accordance with the Crosbie et al patent, wherein reaction product solids become entrained in a gaseous outflow from a reaction situs, to recover such reaction product solids. This and other objects and advantages of the present invention will be better understood from the following disclosure and discussion of the invention.